The present invention is directed to devices for pressing a packing or covering or dressing, such as a forme or a blanket on a cylinder. A plurality of rollers are used to either install or to remove a dressing. A single or shared adjusting mechanism is provided to move the rollers.
U.S. Pat. No. 3,828,672 A discloses a device for pressing a printing plate against a plate cylinder. For installation and removal of the printing plate, a roller, which extends parallel to the cylinder axis and which also extends over the entire plate width, is pivoted toward the cylinder by the use of two arms and is pressed against the plate cylinder by a hydraulic working cylinder.
EP 07 12 725 B1 discloses a device that is usable for pressing against printing plates with the aid of a number of rollers which are disposed along the cylinder circumference, and which do not extend over the entire plate width or the cylinder length. These rollers are placed individually or in pairs against the plate cylinder by the use of a piston rod of a working cylinder. The device has two such roller systems that are disposed next to each other and that are in engagement with each other. Each system is comprised of several rollers and associated working cylinders. The first system is used, for example for installing a new printing plate, and the second system is used for removing a dirty printing plate. In order to protect the apparatus from getting dirty, opening flaps are provided in the movement region of the rollers and can be actuated by the provision of separate working cylinders.
EP 04 33 798 B1 has a pivotable guard for a changing device of a printing plate which pivotable guard protects the entire apparatus that is oriented toward the access side from getting dirty. The pressing roller is a one piece roller, and working cylinders situated at both ends of the roller place it against the cylinder by use of a lever. In a similar manner, in EP 04 35 413 A2, a number of rollers, which are disposed on an axle, are placed against the cylinder as a group by the use of a two-arm lever which is driven by a working cylinder in order to guide the plate end into the cylinder channel during plate installation.
U.S. Pat. No. 4,727,807 A shows a device for installing and removing printing plates from plate cylinders by the use of a pivotable gripping arm. A number of rollers, which are spaced apart from each other in the circumference direction of the cylinder and which are situated next to each other in the longitudinal direction of the cylinder, are placed against the cylinder both for installing and removing the plate.
The object of the present invention is to produce devices for pressing on a dressing, packing or cover to place the dressing, packing or cover on a surface of a cylinder or to remove the dressing, packing or cover from the surface of the cylinder.
The object is attained according to the present invention by the use of a number of rollers that can be placed against the surface of the cylinder. At least two rollers are supported independently of each other and can each be placed against the cylinder by a single adjusting mechanism. At least one roller is used during dressing, packing or cover installation and the other is used during dressing, packing or cover removal. The rollers are positioned one after the other in a circumferential direction of the cylinder. Both are driven by a shared adjusting mechanism.
The advantages that can be attained with the present invention are comprised particularly in that a number of rollers, which can move independently of one another, are actuated by a single mechanism and are selectively pressed against the cylinder. Each roller is actuated directly and with the same force. The force can be adjusted easily by the use of a uniform pressure level. This assures a uniform pressure of a dressing, packing or cover on a cylinder. The rollers are supported at least partially independently of one another, which independent support permits a mutually independent movement of the rollers at least in the direction toward the cylinder.
The present invention is not sensitive to deviations in the position of the device in relation to the cylinder and in relation to a deflection. This allows for a simple and a compact design, which, for statics-related reasons, is only possible at a greater expense when a single roller is provided that extends continuously over a plate or over the width of a cylinder.
It is also particularly advantageous that despite the direct deployment of each of the individual rollers, only a single adjusting mechanism is required for a group of rollers. This results in considerable savings with regard to drive technology and with regard to regulating and control costs.
The stroke of the adjusting mechanism can be easily increased as needed for each roller by the use of a stroke multiplication linkage so that, for example, the device can be disposed in a stationary fashion and does not have to be moved as a whole in relation to the cylinder.
In a simple manner, the device for pressing a dressing, packing or cover on a cylinder in accordance with the present invention can also be embodied so that for the installation and for the removal of dressing, packing or cover, different respective rollers are placed against the cylinder. This has the advantage that during blanket or plate changing, new blankets or plates to be installed on the cylinder do not get smudged by already dirty rollers that were used for the removal of prior blankets or plates. In an advantageous embodiment, the rollers for installing the dressings, packings or covers, typically in the form of blankets or plates and the rollers for removing them are disposed so that they can be pivoted around an axis, which permits a continuous placement of rollers over the entire width of the blanket or plate or permits the blanket or plate to be pressed against the cylinder at the same respective location.
Flaps, that move synchronously with the rollers, are used to guard the rollers against the possibility of getting dirty when they are in a retracted position. It is particularly advantageous to couple the movable guards to the roller supports that are moved by the adjusting mechanism. When the rollers are deployed, the guards open at the same time, which opening of the flaps or guards involves no further control and drive expense.
For an exact insertion of a leading end of a dressing, packing or cover, such as a blanket or plate, at least one stop is advantageously provided, which is stationary in relation to the machine stand. It is advantageous that when installing the clover, the formation of the stop imparts an initial stress on the leading end, which permits the cover to engage in detent fashion in the provided clamping or tensioning device in a manner that is reproducible because it is guided.